At some point I heard that tandems should have wider handlebars for "control".
After many years of riding 42cm bars and being uncomfortable, I switched to my normal 40 and that was much better.
Mavic SSC brakes are a great option for tandem caliper brakes. They can be a bit difficult to find though. Also they don't have a release mechanism so it may be difficult to get the wheels off unless you have Campy shifters which have the release built into the brake lever, Shimano does not.